state of libstdcxx_so_7-branch

[Doug Gregor]

On May 3, 2007, at 1:26 PM, Benjamin Kosnik wrote:
> What is your merge/update plan WRT cxx0x-branch and mainline? Do  
> you have a schedule, or a feeling, or what?

I plan to update cxx0x-branch from mainline occasionally (no set  
schedule), just to stay in sync. cxx0x-branch should gather solid C+ 
+0x-related patches as they are posted to the lists, and we'll merge  
individual changes back to mainline when a libstdc++ or C++ FE  
maintainer approves them for mainline.

>> Either way, we should always plan on moving the non-ABI-breaking  
>> features from the cxx0x-branch to mainline. Long before we get  
>> concepts, we'll still want to have library support for rvalue  
>> references, variadic templates, etc. in mainline and under -std=c+ 
>> +0x.
>
> Yes. We should still be pretty aggressive about keeping things in  
> sync I think. We have to take pains to minimize divergence, since  
> this is potentially a long-lived branch.

Agreed.

> I think we want something stronger, actually: I think we should  
> make every effort to make cxx0x and mainline testsuites match, at  
> least on a file-per-file basis. (There will be some xfailing, etc.)

Also agreed. This is also important because the C++0x branch tests  
the C++0x compiler and library much more heavily than the mainline  
compiler, because *everything* is run under C++0x mode by default.

> That way the merges only have to deal with the rest of this stuff.

Yep.

So, does this mean that cxx0x-branch should have libstdc++-v4, the C+ 
+0x libstdc++? We could retain libstdc++-v3 as the C++98/03 standard  
library implementation (with some non-ABI-breaking C++0x features, of  
course), and make libstdc++-v4 the C++0x library. We'll have to  
maintain both libraries for a long time, but I suspect it will be  
easier in the long run.

If this is the way to go, and I think it is, then I'm certainly not  
the best person to make this change. Someone with a better  
understanding of the configure logic, header install process, etc.  
should handle the initial setup of libstdc++-v4.

	- Doug